With all the NoSQL hotness out
there, believe it or not, some people are still using relational
databases. (I know, right?).

When it comes to dealing with schema changes, the Active Record
Migrations in Rails make schema changes so easy, developers often take
them for granted. However, for extremely large sets of data, running an
ALTER TABLE might mean taking your database offline for hours. After
considering otherprojectsRany
Keddo and the smart folks at
Soundcloud developed their own solution.